Coding & Algorithms Interview Questions
Practice 3,469 real Coding & Algorithms interview questions for 2026. Covers companies like Meta, Amazon, Google, Uber, and Microsoft. Real questions from actual interviews with detailed solutions — ideal for focused interview preparation. Coding & Algorithms interview questions are the single most common technical gate for software engineering roles and are used to evaluate problem framing, algorithm selection, complexity trade-offs, correctness, edge-case reasoning, and clear communication under time pressure. Expect this category to appear in early technical screens and repeatedly across onsite loops at companies that weight it heavily (notably Meta, Google, and Amazon). Interviews will test arrays and strings, trees and graphs, dynamic programming, hashing and two‑pointer techniques, and the candidate’s ability to test and optimize code in a shared editor. Prepare with timed mock interviews, practice in the same editor you’ll use live, and build a progressive schedule that moves from fundamentals to medium/hard problems; typical candidates invest several weeks to a few months of focused practice depending on seniority and target company.
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"Literally just signed a $600k offer. I only had 2 weeks to prep, so I focused entirely on the company-tagged lists here. If you're targeting L5+, don't overthink it."
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"I honestly don't know how you guys gather so many real interview questions. It's almost scary. I walked into my Amazon loop and recognized 3 out of 4 problems from your database."
"Discovered PracHub 10 days before my interview. By day 5, I stopped being nervous. By interview day, I was actually excited to show what I knew."
"I recently cleared Uber interviews (strong hire in the design round) and all the questions were present in prachub."
"The search is what sold me. I typed in a really niche DP problem I got asked last year and it actually came up, full breakdown and everything. These guys are clearly updating it constantly."
Implement Trie search with wildcard matching
Design a text dictionary using a Trie. Support the following operations: - addWord(word): Insert a lowercase English word. - search(pattern): Return t...
Find spammer with minimal hasMessaged calls
Question You have n accounts labeled 0..n-1 and an oracle API: ` boolean hasMessaged(a, b) // true iff account a has sent at least one message to ac...
Implement an extensible prefix tree
Implement a prefix tree (trie) supporting insert(word), search(word), startsWith(prefix), countPrefix(prefix), and erase(word). Optimize for time and ...
Implement sparse vector dot product
Question Design a SparseVector class for vectors of integers in which most entries are zero, and support an efficient dot product between two such vec...
Compute BST range sum
Given the root of a binary search tree and two integers low and high (inclusive), compute the sum of values of all nodes with low <= val <= high. Prov...
Evaluate arithmetic expression with variables
Implement an expression evaluator for a string expr containing non-negative integers, variables (alphabetic names), operators +, -, , /, parentheses '...
Compute task order with prerequisites
Given an integer n representing tasks labeled 0..n-1 and a list of prerequisite pairs (a, b) meaning b must be completed before a, return any valid or...
Maximize profit with bounded sell window
Given an array prices[0..n-1] of daily stock prices and an integer D ≥ 1, you may perform at most one transaction (buy then sell). The sell day j must...
Decide and implement DP/heap and approximation
You have 90 minutes to complete three related coding tasks: a) Dynamic programming: Given an integer array nums (n ≤ 2e 5) and a threshold T, design a...
Find nearest room; extend to two users
You are given an m×n grid where 1 is a wall (impassable), 0 is an empty cell, and 2 is a meeting room. From a starting coordinate [r, c], you may move...
Compute product excluding index without division
Given an integer array nums, return an array ans where ans[i] equals the product of all elements of nums except nums[i], without using division. Achie...
Implement tree left/right views via BFS and DFS
Given a binary tree, output the left view and right view: for each depth, the first node visible from the left and the first node visible from the rig...
Solve array and tree algorithm challenges
Solve the following three algorithmic tasks: 1) Unique triplet sum: Given an integer array nums and an integer target (default 0), return all unique t...
Solve windowed duplicates and target expression
1) Windowed duplicate check: Given an integer array nums and an integer k, determine whether there exist indices i and j such that nums[i] == nums[j] ...
Count islands with eight-direction adjacency
You are given an m×n grid of characters '1' (land) and '0' (water). Count the number of islands, where cells are connected if they touch in any of the...
Maximize equal values via one subarray shift
Given an integer array A of length n, you may perform at most one operation: choose any contiguous subarray A[l..r] and add an integer Δ (which may be...
Maximize points with limited coworker skips
You and a coworker must unload a sequence of warehouses. For warehouse i there are c[i] items (non‑negative integers). Turns alternate starting with y...
Validate and restore IPv4 addresses
Design and implement the following IPv4 tasks. a) Validate dotted IPv4: Write a function isValidIPv4 (s) that returns true if s is a valid dotted-deci...
Solve four algorithm design tasks
Solve the following four algorithmic tasks: 1) Implement wildcard pattern matcher: Given a text s and a pattern p where '?' matches any single charact...
Find value on most distinct levels
Given a binary tree whose nodes store values (e.g., characters), find the value that appears on the greatest number of distinct depth levels. For exam...